Electrical control for power presses



Nov. 23, 1954 G. l. DANLY ETAL 2,695,383

ELECTRICAL CONTROL FOR POWER PRESSES Filed April 6, 1950 4 Sheets-Sheet 1 P15 .1. kilo 54 o 5/0 504 fA/VEA/TOPS 53o GEORGE I Omar 5% James C. ,D/QA/LY BEA-CHER 5. JED/v55 528 TTORNEY Nov. 23, 1954 G. l. DANLY ETAL 2,695,383

ELECTRICAL CONTROL FOR POWER PRESSES Filed April 6. 1950 4 Sheets-Sheet 2 1' MAIN MOTORO uP I new: 7

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F Y E INVFA/TOES Geoes I DAM/LY @0755 C, Dg/vLyr BEECHEE 5. o/vss BM 5 A (SRNEY United States Patent ELECTRICAL CONTROL FOR POWER PRESSES George I. Danly, Elmhurst, Beecher B. Jones,'Chicago, and James C. Danly, River Forest, Ill., assignors to Danly Machine Specialties, Inc., Chicago, 111., a corporation of Illinois Application April 6, 1959, Serial No. 154,362

9 Claims. (Cl. 318-365) Our invention relates to electrical controls for power presses.

Power presses are large and heavy pieces of machinery in which metal sheets are formed in dies under heavy pressure. The energy for the working cycle of the press is stored in a flywheel which is constantly running. The working train of the press is normally immobilized by a brake. When it is desired to place the press into operation. the flywheel is clutched to the working train of the press and the brake is simultaneously released. This is accomplished through fluid pressure such as air pressure applied to a cylinder to release the brake against the action of springs and simultaneously applied to a clutch air cylinder to engage the clutch against the action of springs normally moving the clutch to released position. The opening of the valves which place the clutch and brake in communication with a source of compressed air is controlled by solenoids, the windings of which are simultaneously energized by a control system. it is this control system to which our invention relates.

A control system for a power press must have absolute safety for the operating personnel. Many press operators have been maimed for life by the loss of fingers or of hands due to the inadvertent operation of the press during the manual removal of or insertion of work to the press dies. Accidents occur too during the adjustment of the dies which may result in injury to operating personnel as well as to injury to the press. Accidents are frequently due to faulty operation of the press control by which the press is set into operation due to failure of the control in various respects.

In the electrical control systems for power presses in the prior art a plurality of run buttons is provided so that if the type of work being performed by the press requires a plurality of operators the press will not run unless each of the operators has both hands on the run 1 buttons provided for this purpose. The press control, however, is designed so that the run buttons may be locked in or bridged so that for other types of work run buttons may be eliminated. There have been cases where all of the run buttons have been locked in and i an operator operates the press by use of the stop button so that the press will run whenever the stop button is released and will stop when the stop button is operated. This is a dangerous practice and frequently causes injuries.

In the press controls of the prior art it is possible to stop the press just at bottom dead center. Normally the energy of the flywheel is sulficient to carry the press through bottom dead center as long as the brake does not set. If, however, the brake is applied to stop the press just at bottom dead center with work in the press the press becomes frozen. This is known as sticking a press, and it is frequently impossible to jar the press loose by means of the press drive even when running it at speeds considerable higher than those for which the press was designed. When a press is stuck it is frequently necessary to heat the rods and to cut the dies to fre the press. This is an expensive and time-consuming procedure. ,Dies, for example, may cost as much as $20,060. As the press is part of a production line the cost or" down time may be as much as $1,800 an hour and the press maybe down for several days.

vOne object of our invention is to. provide an electrical control for power presses in which absolute safety for the operator is insured.

Another object of our invention is to provide an electrical press control in which the solenoids for operating the brake and clutch are operated from a comparatively high voltage, insuring against excessively high currents, and in which the control circuit is excited by a comparatively low voltage thus protecting the operating personnel from dangerous electrical shocks due to elevated voltages.

Another object of our invention is to provide a control system in which all control currents will flow to ground from a single wire system thus insuring that the press will not operate inadvertently by an accidental ground.

Another object of our invention is to provide an electrical press control in which excessively high currents are avoided at all push button stations.

Another object of our invention is to provide an electrical control for power presses in which operators are precluded from the dangerous practice of tying down the inch button to cause the press to run constantly and using the stop buttons to perform the inching operation.

Another object of our invention is to provide a control which is certain in operation and which combines maximum safety with flexibility.

Another object of our invention is to provide a press in which the clutch is inoperative whenever the slide is being adjusted.

Another object of our invention is to provide a press control circuit in which the clutch is inoperative except for inching when the main motor is not running or when the main motor is running in a reverse direction.

Another object of our invention is to provide an electrical control for power presses which will prevent stalling of the fly wheel at the bottom dead center of the stroke in the event the main motor is cut off.

Another object of our invention is to provide an electrical control for power presses in which operators are precluded from bridging the run buttons and operating the press by means of the stop button.

Other and further objects of our invention will appear from the following description:

In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith, and in which like reference numerals are used to indicate like parts in the various views:

Fig. 1 is a diagrammatic view showing an electrical press control containing one embodiment of our invention.

Fig. 2 is an elevation of the control panel of the electrical press control shown in Fig. 1.

Fig. 3 is a diagrammatic view showing the contacts made at various positions of a key controlled selector switch shown in Fig. 2.

Fig. 4 is a diagrammatic view showing the phase relationships of the operation of rotary limit switches forming part of our control.

Fig. 5 is a simplified diagrammatic view showing a press control circuit generally similar to that of Fig. 1 containing a modification for preventing the press from sticking at bottom dead center in the event the main motor cuts off.

Fig. 6 is a diagrammatic view similar to Fig. 4 showing the phase relationships of the operation of the rotary .limit switches forming part of the control shown in Fig. 5.

Fig. 7 is a simplified diagrammatic view similar to Fig. 5 showing the circuits involved which prevent bridging the run buttons and operating the press by means of the stop button.

Referring now to Fig. 1, a line voltage is introduced to posts 10 and 12 through conductors 14 and 16. This voltage may be an elevated voltage such as 440 volts. A circuit breaker 18 is interposed in the line 14 and a corresponding circuit breaker 20 is interposed in the line 16. The primary winding 21 of a step-down transformer is placed across the line by conductors 22 and 24. A first air valve solenoid winding 26 and a second air valve solenoidwinding 28 are adapted to be connected in parallel across the main line by the controlvcircuit. A conductor 30 connects, conductor 32 to the main line 14 through a .fuse.34. The conductor 32 terminates. in a pairv of contact points 36and 38 connected in parallel.

These are adapted to be connected to contact points and 42 by the conducting armature 44 of a relay 46. When the relay is operated the conductor 32 will be connected through the relay armature to conductor 48. It will be noted that there are two pairs of contact points in parallel so that the connection will be made with absolute certainty. Conductor 48 is connected by conductor 50 to both windings 26 and 28, the other ends of which are connected by conductor 52 to conductor 54. This conductor terminates in a pair of contact points 56 and 58 connected in parallel and adapted to be connected by the armature 60 of a relay 62 to contact points 64 and 66, thus completing the circuits across solenoid windings 26 and 28 through conductor 70, which may contain fuse 72, to the other side of the line. The arrangement is such that when both relays 46 and 62 are operated the circuit is completed through solenoid windings 26 and 28 to operate the control air valve. When the windings 26 and 28 are de-energized by the opening of the circuit at either between conductors 32 and 48 or conductors 68 and 54, the press will be stopped by the closing of the air valve.

It will be observed that the clutch solenoid circuit is broken on both sides by the control relays and that the clutch is rendered inoperative and the brake set even though either of the two control relays should stick closed.

The primary winding 21 of the transformer indicated generally by the reference numeral 74 is inductively coupled to the secondary winding 76. One end of the secondary winding 76 is connected by conductor 78 to ground 80. The other end of secondary winding 76 is connected by conductor 82 to the hot wire 84 through a fuse 86. A conductor 88 is connected to one side of an incandescent lamp 90. The other side of the mean descent lamp is connected by conductor 92 to the ground wire 94 which is connected to ground through conductor 98.

The transformer 74 steps down the voltage from 440 volts to volts, so that the control system is operated at a reduced voltage to protect the operating personnel. The use of a single wire system accomplished by the grounding of the secondary winding 76 at ground 80 prevents the press from repeating or operating due to a ground anywhere in the circuit. If a ground of sufiicient magnitude occurs anywhere in the control circuit which could operate any of the relays, a short circuit is automatically created of a suflicient magnitude to blow one of the protective fuses or open the circuit breakers of the main power supply.

A conductor 100 is connected to a contact point 102 which is adapted to be connected to contact point 104 by the armature 106 of a lubricant pump starting button 108. The pressing of the starting button 108 energizes the relay 112 by completing the circuit through it by means of conductor 114 and ground wire 94 and attracting armature 116. When this occurs current will flow from conductor 122 to contact point 118 and thence to contact point 120 and conductor 124 to conductor 126 through stop button 130 through conductor 128 and thence through the winding of relay 112 to ground. It will be seen that this forms a holding circuit maintaining the relay 112 energized after the starting button 108 is released. This holding circuit can be broken by pressing the stop button 130. The operation of the relay 112 also completes the circuit from conductor 122 through the lubricating pump motor control 110 through conductor 92 to ground, thus starting the lubricating pump motor (not shown). This motor is connected across the 440 volt line and drives shaft 132 to drive oil pump 134 to which oil is fed through intake pipe 136 from a suitable oil reservoir (not shown). The oil pumped by oil pump 134 discharges through a manifold 140. A branch pipe 142 communicates the oil discharge pressure to the interior of a cylinder 144 in which we position a piston 146 normally urged upwardly by a spring 148. An armature 150 is carried by the piston rod 152 and is adapted to be urged downwardly by the oil pressure acting on ,the piston 146 against the action of spring 148 to bridge the contact points 154 and 156. This connects the hot wire 84 through conductor 158 which is connected through contact points 160 and 162 normally bridged by armature 164, contact points 166 and 168 normally bridged by armature 170, contact points 172 and 174 normally bridged by armature 176. An anti-repeat relay 420 is provided with a pair of contacts 209 and 211 which are normally closed by its armature 418. Contact 211 is connected by conductor 178 to contact point 205. Contact point 209 is connected by conductor 179 to contact point 207. When anti-repeat relay 420 is in the position shown in Fig. l the circuit through relay winding 180 is first completed through the armature 418 of relay 420. When the winding of relay 180 is energized its armature 206 will complete the circuit through the winding 180 across contact points 205 and 207 so that when the anti-repeat relay 420 is later operated it will not break the circuit through relay 180. The arrangement is such that if the anti-repeat relay 420 is stuck open it will be impossible to energize relay winding 180. The armature 164 is controlled by a valve arrangement within the housing 184, the armature is controlled by a valve arrangement within the housing 186, and the armature 176 is controlled by a valve arrangement within the housing 188. Oil is supplied to the housing 184 through branch pipe 190 and discharges from the housing through pipe 192 leading to a bearing of the press. Oil is supplied by a branch pipe 194 from the manifold 140 to the housing 186 and is discharged through branch pipe 196 to another press part. Similarly, oil is supplied by a branch pipe 198 from the manifold 140 to the housing 188 and is discharged through a pipe 200 to another press part. The arrangement of the valves within the housings 184, 186 and 188 is such that upon clogging of the oil supply to the bearings the armature associated with the housing to which the oil supply is diminished or from which the oil supply is diminished through clogging will move downwardly, as shown in the drawings, to open the circuit through the relay winding 180. The construction of the valve arrangement forms no part of the instant invention but is shown and described in co-pending application of Vasil Georgeff, Serial No. 118,540, filed September 29, 1949, now Patent No. 2,688,382. Similarly if the oil pump 134 loses suction so that the oil supply fails, the spring 148 will move the armature 150 upwardly opening the circuit across contact points 154 and 156 again opening the circuit through relay winding 180. The hot wire 84 is connected by conductor 202 to contact point 204 which is adapted to be connected by armature 206 associated with the relay winding to contact point 208 so that when the relay winding 180 is energized the conductor 210 is connected to the hot wire 84 through conductor 202. The conductor 210 is connected to the conductor 212 which becomes a hot wire whenever the relay winding 180 is energized.

The switch arm 214 is a key controlled member adapted to be locked by a key on'the control panel shown in Fig. 2, either in the full line position shown in the drawing connecting conductor 216 to contact point 218 or in the dotted line position connecting conductor 216 to contact point 220. This switch arm controls the direction of rotation of the main motor. The key controlled switch is operated by key inserted through keyhole 221, shown in Fig. 2, to be positioned in either the forward or reverse position. The circuit from the hot wire 212 to the ground wire 94 through the main motor control relay 240 is first made by operating the starting button 224 which appears on the main control panel shown in Fig. 2. Let us assume that the switch arm 214 is in the position shown in the full lines in the drawing, that is, to operate the main motor in the reverse direction. When the starting button is pressed current will flow from the hot wire 212 through conductor 226 across contact points 228 and 230 through the armature 232 of the starting button, thence across the armature 234 of the stop button 236 which is normally closed, through conductor 216 through switch arm 214 to contact point 218 through conductor 238 through the winding of relay 240 through conductor 242 to the ground wire 94. The energization of the winding of the relay 240 will raise its armature 246 to complete the circuit across contact points 248 and 250 which are normally open. When this occurs current will flow from the hot wire through conductor 226 through conductor 252 to contact point 248 through armature 246 to contact point 250 through conductor 254 across the stop armature through conductor 216 and thence through the holding relay 240 to ground. This current will continue to flow due to the action of the holding relay, just described, after the starting button armature 232 breaks contact across contact points 228 and 230. The upward movement of the armature 246 completes the circuit from conductor 210 across a pair of contact points closed by the armature 246 through conductor 221 thence through main motor reverse control 222 through conductor 224 to ground. The energization of the main motor control 222 operates the main motor (not shown) to run in the reverse direction. This motor is energized by the high voltage power supply. The pressing of the stop button interrupts the circuit through the holding relay 249. When the key operated switch arm 2114 is moved to dotted line position the current will flow through the switch arm to contact point 220 and thence through conductor 256 through holding relay winding 253 through conductor 260. The energization of the relay winding 258 will raise its armature 262 bridging the contact across contact points 264 and 266 so that current will flow from the hot wire 212 through conductor 226 through conductor 252 from contact point 264 through the armature 262 to contact point 266, and thence through conductor 254 across the stop button armature 234 through arm 214 to contact point 226, and thence through the holding relay winding 258 and conductor 269 to ground. The holding relay 253 is similar to the holding relay 240, maintaining the holding relay 258 energized after the release of the starting button 224. The energization of the winding 258 will cause the armature 262 to bridge contact points 263 and 265 completing the circuit from conductor 252 through conductor 267 through main motor forward control 223 thence through conductor 243 to ground wire 94, causing the motor to run in the iorward direction. The movement of the armature 262 under the influence of the energize relay winding 258 will also bridge a circuit across contact points 268 and 276 connecting a part of the control circuit to the hot wire when the main motor is energized to run in a forward direction, as will be pointed out more fully hereinafter.

The hot Wire 2112 terminates at a binding post 272 to which is connected a key controlled switch arm 274. This switch arm controls the energy for the slide adjustment motor. When the key controlled arm 274 is in the position shown in the full lines in Fig. 1, it is in the slide adjustment motor off position. The key inserted in slot 273 and turned to the off position will connect the hot wire 212 to the conductor 276. When the key is in the dotted line position shown in Fig. 1, the switch arm 2'74 connects the hot wire binding post 272 to the contact point 273. If the slide adjustment motor up button 236 is pressed, its armature 282 will make a circuit across contact points 234 and 286 and across contact points 288 and 29% which are normally closed by the armature 292 of a down relay winding 294. An up limit switch operated by a cam 318 has its armature 364 in a position normally bridging its contact points. The current will then flow through conductor 2% through the up relay winding 293, and thence through conductor 366 and conductor 362 to ground. The energization of the relay winding 2% raises the armature 312 and breaks the normally closed circuit across contact points .314 and 316, through which the down relay winding 294 is energized. The energization of the slide adjustment up relay 298 will cause its armature 312 to complete a circuit through slide adjustment up motor control 331 causing the slide adiustment motor to run in the upward direction. If the slide moves upwardly too far the cam 318 actuated as a function of movement of the slide in the upward direction will break the circuit by depressing armature 304, thus protecting the slide and the press parts. in this manner the pressing of the button 280 will cause the slide adjustment motor to run upwardly. The motor will run only when the normally opened button 236 is pressed. The closing of the circuit across contact points 320 and 322 through armature 324 controlled by button 326 will cause current to flow through conductor 328 across armature 312 which is normally closed, through the down relay winding 294 through conductor 302 to ground, it being understood that the slide adjustment down limit switch 308 operated by the earn 332 is in a position bridging its contacts thus closing the circuit. The energization of the winding 234 raises the armature 292 and opens the circuit controlled by the up push button 236. The arrangement is such that both push buttons cannot be simultaneously operated and the operation of one precludes the operation of the other. The energization of the winding of the down slide adjustment holding relay 294 will raise its armature 292 pair of contact points through down control 333 causing the slide adjustment motor to run in the downward direction. The slide adjustment motor will run in the downward direction only as long as the circuit is closed across contact points 320 and 322 by the actuation of the down push button 326. The movement of the slide downwardly will operate a cam 332 which will open the circuit by lifting armature 308 when the slide reaches a predetermined limit position in the downward direction. The slide adjustments are made for various thicknesses of dies or various thicknesses of work to be used in the press. The energization of the slide adjustment motor automatically de-energizes thecontrol system for operating the clutch and brake since the key operated switch 274 automatically breaks the control circuit when the slide adjustment motor circuit is energized.

When the slide adjustment motor switch arm 274 is in the slide adjustment olf position, conductor 276 be comes energized, that is, hot. This conductor terminates in a contact point 334 adapted to be connected by an armature 336 to contact point 338. The pipe 346 represents the fluid pressure manifold which supplies fluid presusre, such as'compressed air, to the clutch and brake cylinders. If the air pressure is insufficient to safely operate the clutch and brake, the circuit across contact points 334 and 338 is broken. The armature 336 is connected to the piston rod 342 of a piston 344 positioned within a cylinder 346 to which a branch pipe 348 introduces the compressed air. A spring 350 normally urges the piston 344 to open the circuit across contact points 334 and 338. When the air pressure is sufficiently high safely to operate the clutch and brake, the piston 344 moves against the action of spring 356 to make the circuit across contact points 334 and 338 through the armature 336 This energizes the conductor 352 which term1nates 1n a contact point 354 adapted to be connected by armature A to contact point 356, thus energizing conductor 353 and conductor 360 across stop button 362 and its associated armature. The stop button 362 is placed at a convenient position on the press and it is this stop button which is frequently used in other control systems for inching but which cannot be used for this purpose in our system, as will be pointed out more fully hereinafter. Conductor 360 energizes the inching section of the control. The closing of the circuit across contact points 354 and 356 by armature A also energizes conductor 364 across the stop button armature.

Conductor 364 terminates in contact point 268 which when the main motor is energized in the forward position will be connected by the main motor forward relay armature 262 to contact point 270 thus connecting conductor 366 to the hot side of the line. it is only when the main motor is running in the forward direction that the main control panel is energized through the energization of conductor 366.

Referring now to Figs. 2 and 3, it will be noted that there is a key controlled controller switch adapted to be positioned by a key inserted through keyhole 363 to position the switch in one of five positions, namely, momentary, long, off," continuous, and inching.

Referring now to Fig. 1, it will be observed there are six armatures, designated A, B, C, D, E, and F. When the main controller switch is in the off position it will be noted from Fig. 3 that all of the armatures A, B, C, D, E, and F are in an open position, that is, the circuit is broken across the contact points they are adapted respectively to brid e. When the key switch is in the position of momentary, the armatures A, B and C are closed and armatures D, E and F are open. When the switch is in the position long, armatures A, B and D are closed and armatures C, E and F are open. When the key is in the position of continuous. armatures A, B and E are closed and armatures C, D and F are open. When the key is in the position of inching, armatures A and F are closed and armatures B, C, D and E are open. in the off position, armature A will be open as will all of the other armatures. The opening of armature A immediately de-energizes all of the clutch cotrol circuits, both the press operating circuit and the inching circuit.

One of the press shafts 370 carries a plurality of limit switch cams, namely, 372, 374 and 376. Cam 372 is adapted to close the circuit across contact points 378 and 330. Limit switch cam 374 is adapted to close a circuit across contact points 382 and 384. Limit switch cam to close the circuit across a the slide adjustment motor 376 is adapted to close a circuit across contact points 386 and 388. The development of the cam action is shown in Fig. 4, in which the shaded portions indicate the angular position of the rotation of shaft 370 in which the cams act to close the circuits across their respective contact points and the clear portions show the angular positions of the rotation of the cams when the circuits are adapted to be interrupted through the cam action. The three cams rotate in phase with each other and in proper phase relation with the movement of the press slide. The zero degrees indicates top dead center of the press slide and the 180 indicates bottom dead center of the press slide.

Let us assume that we have set the key controlled switch to the momentary position, so that armatures A, B and C are closed, and let us assume further that the main motor is running in the forward direction so that Wire 366 is now connected to the hot side of the line, current will flow from conductor 366 through the armature 390 of a run button 392 through the armature 394 of a second run button 396 through conductor 398 to contact point 402, thence through the armature 60 of the relay 62 to contact point 404, thence through conductor 406 to the contact point 408 associated with the armature 44 of the relay 46 to contact point 410. It will be observed that when the relay windings 62 and 46 are de-energized the armature 60 will close the circuit across contact points 402 and 404 and across contact points 408 and 410 respectively. The current will flow from contact point 410 through conductor 412 to the contact point 386 of the cam limit switch 376. By reference to Fig. 4, it will be observed that at top dead center the circuit is completed from contact point 386 to contact point 388 so that this contact point is connected by conductor 414 to the contact point 416 associated with the armature 418 of the relay 420 which, however, is in open position. Current will also flow from the conductor 412 through the conductor 422 through the winding of the relay 420 through conductor 424 to the ground wire 94, thus energizing the relay and lifting the armature 418. This completes the circuit between the contact point 416 and contact point 426 which is connected by conductor 428 to the hot Wire 366. When this occurs current will flow from the hot wire to contact point 426 to contact point 416 through conductor 414 to contact point 388 across the limit switch conductor to contact point 386 to conductor 422 through the relay winding 428 through conductor 424 to the ground wire 94. It will be observed that upon the energization of the circuit the holding relay 420 is energized through the armav ture 68 of relay 62 and the armature 44 of relay 46. The energization of the holding relay establishes a second energizing circuit which includes the cam limit switch 376 in the circuit. It will be noted that the energization of relay 420 will also complete the circuit across contact I points 430 and 432. These contact points are positioned to interrupt the run circuit adap ed to be completed by pressing both run buttons 392 and 396. If the holding circuit were not resent the initial pressing of the run buttons would de-energize the winding 420 and the run circuit could never be completed. 9

Considering now the run circuit, contact points 434 and 436 are adapted to be brid ed by armature 398 associated with the run button 392 and contact points 438 and 440 are adapted to be bridged by the armature 394 of the run button 396. It will be noted too that in order to initiate the action of the press an operator must press both run buttons 392 and 396. These run buttons are positioned physically a suflicient distance apart so that the operator must use both hands to press them. This precludes any danger that the operator will have one of his hands positioned in the place of danger by the operation of the press. When both run buttons are pressed the initial path of current flow through the winding of relay 420 is interrupted but the current continues to flow through the holding circuit described above. When the armature 390 brid es contact points 434 and 436 and the armature 394 brid es contact points 438 and 440 current will flow from the hot wire through conductor 442 through conductor 444 to contact point 430 through the armature 418 to contact point 432 through conductor 446 across armature B which has been closed through conductor 448 through the winding of relay 62 through conductor 400 to the ground wire 94.

Current will also flow from conductor 448 through conductor 450 through conductor 452 through the winding of relay 46 through conductor 454 to the ground wire 94, thus energizing the winding of relay 46 and attracting armature 44. As was pointed out above, the upward movement of both armatures 44 and 60 will complete the circuit through the clutch and brake solenoids 26 and 28 causing the press to run. The upward movement of armature 60 bridges contact point 458 with contact point 460. The upward movement of armature 44 connects contact point 462 with contact point 464. Potential from the hot wire 366 will, when these events occur, be impressed through conductor 466 through conductor 468 to contact point 458 through armature 66 to contact point 466 through conductor 470 to contact point 462 across armature 44 to contact point 464 through conductor 472 through conductor 474 to contact point 384. When the press is at top dead center the cir cuit from contact point 384 to contact point 382 is open. As soon as the press starts to run, however, through a very short angle of rotation of the cam 374, say about 5, the cam switch 374 will complete the circuit from contact point 384 to contact point 382 across armature C which is also closed in the momentary position, so that current will flow through conductor 47 6 to conductor 452 through the winding 46 through conductor 454 to the ground wire 94. Current will also flow from conductor 476 through conductor 450 upwardly through conductor 448 through the winding 62 through conductor 400 to the ground wire 94. It will be seen that as soon as the limit switch 374 completes the circuit across contact points 384 and 382 that both relay windings 62 and 46 are energized independently of the run buttons which started the press. Accordingly, after the press is operated through 5 of its working cycle the run buttons 392 and 396 may be released and the press will run controlled through a circuit completed by the limit switch 374. This is the momentary condition in which an operator may start the press and then remove his hands from the run buttons. This condition cannot be brought about without setting the key controlled switch by the inser tion of a key through key slot 368, shown in Fig. 2, and setting the pointer 367 to the momentary position. The operator cannot do this at will since only the foreman or other person in authority can set the key operated master control switch, and when this is done a person in authority takes the responsibility for setting the press in this condition. The press will continue to run until the rotary cam switch 374 reaches a position of about 10 before top dead center. As will be seen by reference to Fig. 4. the conducting circuit across contact points 384 and 382 is then broken. This immediately de-energizes both windings 62 and 46 permitting the armature 66 to break the circuit on one side of the solenoid windings 26 and 28 and the armature 44- to break the circuit across the other side of the solenoid windings 26 and 28. At the same time the circuit across contact points 458 and 460 is opened by the dropping of armature 60 and the circuit across contact points 462 and 464 is broken by the dropping of armature 44. It will be noted, too, that the run buttons having been released no longer bridge the contact points 434 and 436 and 438 and 440. Simultaneously with the operation of rotary cam 374, rotary cam 376 will open the circuit across contact points 388 and 386 at a point before top dead center. This deener izes the winding of relay 420 which cannot be energized again without releasin the run buttons 392 and 396 to the position shown in Figure 1. The arrangement just described is such that it is impossible to make the press run continuously by holding down both run buttons. since the cam limit switch 376 Will de-energize the holding relay winding 420 and this will break the run circuit across contact points 438 and 432. If the press should coast after cam limit switch 374 breaks the circuit across contact points 382 and 384 and re-establishes the circuit here after it has once been broken, the press will not repeat since the circuit is broken across contact points 458 and 460 as well as across contact points 462 and 464. In the momentary position, therefore, the press will run once and then automatically stop, and it is impossible to make the press run continuously by holding the run buttons down constantly. The run buttons must be released after the time when cam limit switch 376 has interrupted the circuit and then again operated. Since this does not occur until close to top dead center, we insure against any possibility of the press repeating when the key controlled master switch is set in a momentary position.

Lotus now consider the operationof our control with the key controlled master control switch set .in the .long position. This is the norms? safe operating position for the press and is designed to run only as long as the operator presses both run buttonsthrough the major part of the working cycle of the press. In this position armatures A, B and D are closed and armatures C, E and F are open. The holding relay winding 420 is energized as described above. When the run buttons are pressed, the current will flow from the hot wire across the run button contacts across armature B and through winding 62 as pointed out above, and simultaneously through conductor 450 and. conductor 452 through winding 46 as pointed out above. In the long position the armature 60 will close the circuit across contact points 458 and 460 and the armature 44 will close the circuit across contact points 462 and 464 as before. This will energize the conductor 472. The circuit established across contact points 382 and 384 by the rotary cam switch 374, however, will be broken across armature C which is not closed in the long position. Instead a parallel circuit from conductor 472 through conductor 4% to contact point 378 will be established. Thisv circuit is adapted to be completed through contact point 330 conductor 482 and armature D which is closed in the long position, thence through conductor 484 to conductor 459 to conductor 448 and through relay winding 62, as well as through conductor 452 through relay winding 46, when the limit switch 372 closes the circuit across contact points 378 and 380. By reference to Fig. 4 it will be observed that this does not occur until cam limit switch 372 has reached a point adjacent bottom dead center, at which point it is safe for the operator to remove his hands from the run buttons. The arrangement is such that the operator must keep both hands on the run buttons until cam limit switch 372 closes the circuit through the relay windings 62 and 46, as pointed out above. If the operator takes either of his hands from the run buttons until this event occurs both relay windings 62 and 46 will be immediately de-energized. After' the cam limit switch 372 closes the circuit across contact points 378 and 38% the operator may remove his hands and the cycle will continue, as described above in connection with the momentary control. Before top dead center, the cam limit switch 376 will interrupt the holding circuit which will preclude holding the run buttons down continuously and permitting the press to repeat a cycle. Before top dead center is reached the circuit is interrupted across contact points 378 and 380 and the press will coast through a small angle to the top dead center position. it is to be understood, of course, thatthe press will not step without a slight angular motion, due to the fact that the brake cannot be set to stop the press instantaneously. There is a slight angular motion of the press during which the brake brings the press to a stop and the adjustment of parts is such that the moment of rest will occur at top dead center.

In the off position, since armature A is open, all of the control circuits governed by the run buttons are deenergized and it is impossible in this position to run the press. If the wire 366 is grounded, it cannot be connected to the hot side of the line through a ground since this latter ground will blow either fuse 86 or operate one of the circuit breakers 18 or 29 to de-energize the primary winding 21. It will be seen, therefore, that in the off position the press is in safe condition and it is impossible to start the press operating either by a ground or a short circuit.

There are some occasions when it is desired to operate the press continuously and this is accomplished by setting the key operated master control switch to the continuous position. Both armatures A and B are closed and armature E is closed as well. Armature E lay-passes both cam limit switches 372 and 374 in that the circuit through windings 62 and 46 is established from the conductor 472 through armature B through conductor 484, whence current will flow through conductor 45%) through winding 62 and through conductor 452 through winding 46. This will maintain the clutch and brake solenoid windings in energized condition causing the press to run. Since the current supply in this case is from the hot wire through conductor 466 the de-energization of the anti-repeat relay winding 420 through the action of rotary cam switch 376 will have no effect on the continuous running of the press. The press must be stopped after it has been set 10 into operation for. continuous running by the pressing of the stop button 362.

Let us now assume that it is desired to inch the press as is done when adjusting c1" changing dies, die sets, or the like. The master key controlled switch pointer 367 is placed to the inch position. This closes armatures A and F and opens armatures B, C, D and E. The opening, of armature B insures that the operation of the run buttons will not close the circuit through either of the relay windings 62 or 46, so that it will be impossible for the press to run through the actuation of the run buttons when the control is placed in the inch position. The opening of armature C insures that when the relays 62 and 46 are energized by the inching button, the press will not cycle once it starts to run under the influence of the energization of the relays 62 and 46 through the inching button. The interruption of the circuit through armature D insures that when the press is inched by the inching button and the relays 62 and 46 are thus energized, that it will not continue to run. The inching button 500 is located on the main panel, as shown in Fig. 2. As soon as the main key controlled selector switch is placed in the inching position. and the armature F closed, the winding of relay 502 will be energized, current flowing through conductor 504 to the ground wire 94. The energization of the winding of relay 502 will lift armature 5'06 and complete the circuit across contact points 598 and 510. When this occurs current will also flow through conductor 512 to contact point 510 to contact point 508 through the conductors 514 and 516 across the armature F through conductor 518 through the relay winding of relay 502, thence through conductor 564 to ground. This circuit will maintain the relay winding energized after the inching button 500 is pressed. When the inching button is pressed, it will be observed that its armature will break the circuit which initially energized the winding of relay 502. The hot wire 369 is connected to contact 520 through conductor 522. The contact point 524 is connected to contact point 526 by the conductor 523. Under the energization of the winding of relay 502 the armature 566 is adapted to connect contact 526 with contact 530 and this contact is connected by conductor 532 to conductor 484 which is in turn connected to conductors 452 and 450 in parallel. Until the inching button is pressed, however, contact 524 is isolated and no current will flow. When the inching button is pressed, it will make a circuit across contacts 520 and 524 so that current can now flow through conductor 528 to contact point 526 to con tact 530 through conductor 532 through conductor .84 to conductor 452, thence through the winding 46 to ground and simultaneously through conductor 450 to conductor 448, and thence through winding 62 through conductor 460 to ground, energizing the master control relays. As long as the inching button is held pressed the press will continue to run. As soon as the inching button is released the press will immediately stop. As was pointed out above, the hot wire 366 for the control system was energized only when the main motor was made to run in the forward direction. In inching it is frequently desirable to reverse the direction of the main motor. Accordingly, the hot wire 360 which supplies the inching system is connected to conductor 364 which supplies the hot wire 366 through the action of the relay armature 262. In this manner the press is adapted to be inched in either forward or reverse position of control for the rotation of the main motor. The inching button is placed on the main panel which is usually mounted on the column of the press. in the press controls of the prior art it is possible to tie down the inching button, thus causing the press to run continuously, and then interrupt the running of the press by pressing the stop button. There are usually several stop buttons placed in a convenient position adjacent the press, and in this'manner it is possible with the controls of the prior art to inch the press by releasing the stop button and then stopping the press by pressing the stop button. It will be observed that the press stop button 362is placed in the line which supplies the hot wire 360. If in our invention an operator tries to inch the press, as described above, as soon as the stop button is pressed the power to the hot wire 360 is cut off and this de-energizes the holding relay 502 so that the circuit through the inching button will be automatically interrupted, making it impossible to inch the press by tying down the inching button and using the stop button.

It will be, observed that-throughout the specification we have for purposes of clarity described the current as flowing from the hot wire to the ground wire. This is true only during those cycles of the alternating potential when the hot wire is at positive potential. During the second part of the alternating current cycle, the ground will become the hot wire and the current will flow in the opposite direction. The circuits described, however, are

the same and it is to be understood that as in all cases of alternating current the flow of the current will alternate between the wires designated as hot wires and ground.

Referring now to Fig. 5, it will be noted that the circuit there shown is generally similar to that shown in Fig. 1 but illustrated in a simpler and less confusing manner. For example, the two control relays 46 and 62 with which armatures 44 and 60 are associated are shown in the circuits by which they are energized. The armatures, however, are pictured adjacent to the various contact points across which circuits are adapted to be completed upon the energization of the control windings. For example, the circuits through the solenoid winding 26 are broken at the left across contact points 36 and 42 and across contact points 38 and 40. When armature 44 of control relay 46 moves upwardly it is adapted to bridge the circuit across these points. Similarly, the control winding 26 cannot be energized unless the circuits across contact points 64 and 58 and across 66 and 56 are completed. These are adapted to be completed when armature 60, actuated upon the energization of control relay winding 62, moves upwardly as shown in the drawings. Armatures 44 and 60 are represented and numbered similarly in each part of the circuit where the actuation of this armature either completes or breaks the circuit. It will be noted, for example, that in the circuit across the run buttons contact points 408 and 410 are normally bridged by the armature 44 when the winding 46 is de-energized and contact points 402 and 404 are bridged by the armature 60 when the winding of relay 62 is de-energized.

In order to accomplish the purpose of preventing the press from sticking when the main motor cuts out it will be noted that whenever the main motor runs in the reverse direction the relay 240 is energized thus attracting armature 246. When this armature moves upwardly it will break the circuit across key controlled switch points A and B so that it is impossible to energize the anti-repeat relay winding 420 whenever the motor is running in a reverse direction. Whenever this relay is de-energized the control relays cannot be initially energized. Similarly, it will be noted that whenever the main motor is not running in the forward direction the relay winding 258 will be de-energized so that its armature 262 will be in a position to interrupt the circuit across anti-repeat relay 420. Let us assume now that the main motor is energized to run in the forward direction and that the key controlled switch is in the continuous position. As soon as switch points A and B are closed a circuit across the anti-repeat relay 420 is energized thus causing armature 418 to move upwardly making the circuit across contact points 430 and 432 and across the holding circuit contact points 426 and 416. In the continuous position the circuit across switch member E is also made. When the press is started by moving the starting buttons 392 and 396 to close the circuit across contact points 434 and 436 and across contact points 438 and 440 the control relays 46 and 62 are energized thus starting the press by engaging the clutch and releasing the brake through the energization of the solenoids 26. The energization of the control relays causes armature 44 to complete a circuit across contact points 462 and 464 and armature 60 to complete a circuit across contact points 458 and 460 so that as long as the main motor is running in the forward direction the circuit across contact points 373 and 375 will also be made due to the upward movement of the main motor forward relay armature 262. The press will'run continuously until the stop button 362 is used to interrupt the circuit through the control relay windings 46 and 62. When this occurs the circuit through the continuous switch member E is broken across contact points 462 and 464 and across 458 and 460.

It will be noted, too, that in the continuous position if the main motor should cut out, the circuit which maintains the control relays 46 and 62 will be broken across contact points 373 and 375. If this should occur closely adjacent to bottom dead center the result may be that the press will be stuck. In order to preclude this, a rotary limit switch 371 similar to rotary limit switches 372, 374 and 376 shown in Fig. l is connected in parallel across contact points 373 and 375. It will be observed by refer ence to Fig. 6 that the control circuits are maintained in an energized condition from just before bottom dead center to a point just before top dead center. There is suflicient inertia in the flywheel of the press to carry the parts to top dead center as long as the brake is not permitted to engage to stop the press. Accordingly, the press in our arrangement will still complete its cycle through the inertia of the flywheel due to the fact that the control is prevented from operating even if the main motor is cut out in the continuous position. It Will be seen that in the momentary and long positions the effect of cutting out of the main motor will simply be to deenergize the anti-repeat relay at this moment by breaking the circuit across contact points 403 and 405. This has no effect once the control relays 46 and 62 are energized since the circuit will always be maintained either through rotary limit switch 374 in the case of the momentary position or through rotary limit switch 372 in the case of the long position, so that in both these instances even if the main motor does cut out during the cycle the flywheel inertia will still carry the press to its stop position adjacent to top dead center.

Referring now to Fig. 7, which is a simplified diagrammatic view similar to Fig. 5, we have shown a modification making it impossible to bridge all of the run buttons and operate the press by means of the stop button. While we have shown only two run buttons it is to be understood, as is well known in the art, that any number of run buttons may be used in series. Where there are three operators working around a large press, it is customary to provide six run buttons so that all three operators must put their hands on the run buttons to start the press. For some types of work, however, it may be desirable to bridge the run buttons so that only two operators may operate a press, a single operator may operate a press, or if desired, the press may be operated by the use of one hand only, as may be the case where light work is employed and one hand is used for feeding.

When a run button is bridged both the make line and the run line must be bridged. Referring to Fig. 7, for example, if it is desired to bridge run button 392 the circuit across contact points 391 and 393 is completed and the circuit across contact points 434 and 436 is likewise completed. Let us now refer to Fig. 7. If the main motor is running in the forward direction its relay winding 258 will be energized and armature 262 will move upwardly thus bridging the circuit across contact points 261 and 263. The circuit across contact points 395 and 397 is bridged by the run button 396. Since the control relays 46 and 62 are de-energized the circuit across contact points 408 and 410 and a cross 402 and 404 is made by the armatures 44 and 60. This will energize. the winding 421 moving the armature 419 upwardly. When armature 419 moves upwardly it will make the circuit across contact points 421 and 423 through the limit switch 376 and through the winding of the anti-repeat relay 420. When this winding is energized its armature 418 will move upwardly, thus establishing a holding circuit across contact points 426 416. The upward movement of armature 418 will also complete the circuit across contact points 430 and 432. The energization of the winding 421, however, will break the circuit across contact points 425 and 427. The press is now ready to be set into operation by the operation of the single remaining run button 396. When this is moved downwardly the circuit across contact points 395 and 397 is broken thus de-energizing the winding 421. The anti-repeat relay 420, however, is still maintained energized through its holding circuit across contact points 426 and 416. The de-energization of winding 421 recompletes'the circuit across contact points 425 and 427 so that as the run button 392 is continued to be moved down the circuit through the control relays 46 and 62 is completed across contact points 438 and 440. If, however, it is attempted to bridge the last run button, safety relay 421 remains energized so that its armature 419 will cause the circuit through the control relays to remain open across contact points 425 and 427. It will be seen, therefore, that if it is attempted to bridge all of the run buttons with the view of operating the press by means of the stop button 362 it will be impossible to energize the control relays.

It will be noted that in Fig. 5 and Fig. 7 we have provided a, slightly different circuit for inching so that the press cannot be operated in the slide adjusting position. The switch 274 is moved to the right whenever it is desired to place the slide adjusting in the on position. This ordinarily isolates the entire control circuit so that the press cannot be operated. Whenever the switch member 274 is moved to the left the control circuit is energized and the slide adjusting circuit is automatically deenergized. In other words, the arrangement is such that the slide cannot be adjusted when the press control is in operative condition and the press cannot be operated when the switch is in the slide adjusting position.

It will be seen that we have accomplished the objects of our invention. We have provided an electrical control for power presses in which absolute safety for the operator is insured. We have provided an electrical press control in which the solenoids for operating the brake and clutch assemblies are subjected to a comparatively high voltage, insuring against excessively high currents, in which the control circuit itself is excited by comparatively low voltage in order to protect operating personnel from dangerous electrical shocks. We have provided a control system in which all control currents flow between a hot wire and ground in a single wire system, thus insuring that the press cannot be operated inadvertently by an accidental ground. We have provided an electrical press control in which excessively high currents are avoided at push button stations, thus reducing the danger of freezing contact points of the push buttons. We have provided an electrical. control for power presses in which operators are precluded from practicing the dangerous operation of tying down the inch button to cause the press to run and then using the stop button to perform the inching operation. We have provided a press control in which certainty in operation is combined with maximum safety and flexibility. We have provided a press control which may be set if desired by authorized personnel to conditions not recommended for continuous use where requirements exist for their employment, thus retaining flexibility and insuring maximum safety under these conditions. We have provided a press control circuit in which the press cannot be operated when in slide adjusting position. We have provided a press control circuit which will prevent the stalling of the press at tr e bottom of the stroke in the event the main motor is cut off. We have provided a circuit which will prevent the run buttons from being locked in and using the stop button to operate the press. We have provided a clutch solenoid circuit which is broken on both sides by the con.- trol relays. We have provided a press control circuit which is rendered inoperative except for inching when the main motor is off or when the main motor is running in the reverse direction of rotation.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is Within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, what we claim is:

1. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press, a clutch and brake assembly adapted to be controlled selectively to engage the driving assembly with the clutch or brake of the clutch and brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, a source of potential, a first relay-operated switch for connecting one side of the solenoid to one side of the potential source, a second relay-operated switch for connecting the other side of the solenoid to the other side of the potential source, a first relay winding for controlling the first switch, a second relay winding for controlling the second switch, and. means for connecting said relay windings in parallel with each other and in series with a manually controlled switch across said source of potential.

2. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press, a clutch and brake assembly adapted to be controlled selectively to engage the driving assembly with the clutch or brake of the clutch and brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, a slide for the press, a second motor for adjusting the slide,

a slide adjustment circuit for controlling the slide adjust-' ment motor, a potential source, means for connecting one side of the solenoid to one side of the potential source, a relay-operated switch for connecting the other side of the solenoid to the other side of the potential source, a relay winding connected across the potential source in series with a normally open, manually operable switch and an interlocking switch for selectively energizing the slide adjustment circuit or said relay winding, the construction being such that when the slide adjustment circuit is energized the circuit to the relay winding is automatically broken, and when the circuit to the relay winding is energized the slide adjustment circuit is automatically broken.

3. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press, a clutch and brake assembly adapted to be controlled selectively to engage the driving assembly with the clutch or brake of the clutch and brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, a potential source, means for connecting one side or" the solenoid to one side of the potential source, a normally open relay-operated switch for connecting the other side of the solenoid to the other side of the potential source, a run relay winding for closing when energized the normally open switch, a circuit across the potential source for energizing the run relay winding comprising the run relay winding, a normally open antirepeat relay-operated switch and a normally open, manually operable switch in series across the potential source, an antirepeat relay winding for controlling the first antirepeat switch, a circuit for energizing the antirepeat relay winding comprising a normally closed, manually operable-switch and a normally closed run relay operated switch connected in series across the potential source, a holding shunt circuit for the antirepeat relay winding comprising a normally open second antirepeat relay operated switch and a normally closed first limit switch connected in series across the normally closed, manually operable switch and the normally closed run relay operated switch, and a second holding circuit for maintaining the run relay winding energized comprising a shunt circuit containing a normally open second limit switch connected across the normally open, manually operable switch and the first normally open antirepeat relay operated switch, the first limit switch being set to open momentarily in the fourth quadrant of the press cycle and the second limit switch being set to close in the first quadrant of the press cycle and to open in the fourth quadrant of the press cycle before the reclosing of the first limit switch, the construction being such that an operator is prevented from defeating the purpose of the antirepeat relay by operating the run button before the press cycle has been completed and thus causing the press to run continuously.

4-. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press, a clutch and brake assembly adapted to controlled selectively to engage the driving assembly with the clutch or brake of the clutch and brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, a potential source, means for connecting one end of the solenoid to one side of the potential source, a normally open first run relay-operated switch for conecting the other side of the solenoid to the other side of the potential source, a run relay winding, a circuit comprising a normally open first antirepeat relay-operated switch and a normally open, manually controlled switch connected in series across the potential source for energizing the run relay winding, an antirepeat relay winding, a circuit comprising a normally closed, manually operable switch connected series with the antirepeat relay winding across the potential source for energizing the antirepeat relay winding, a holding circuit for maintaining the antirepeat relay winding encrgized comprising a second normally open antirepeat relay operated switch and a normally closed pressoperated limit switch in series across the normally closed, manually operable switch, a shunt holding circuit for maintaining the run relay winding energized including a second press-operated limit switch and a normally open second run relay operated switch connected in series across the first normally open antirepeat relay operated switch. and the normally open, manually operable switch, the construction being such that in event the second limit switch is closed by the inadvertent travel of the press across top dead center, the momentary de-energization of the run relay will render the run relay holding circuit inoperative.

5. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press, a clutch and brake assembly adapted to be controlled selectively to engage the driving assembly'with the clutch or brake of the clutch and brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, an energizing circuit for the motor, a potential source, means for connecting the energizing I circuit across the potential source, means for connecting one end of the solenoid to one side of the potential source, a normally open relay-operated switch for connecting the other side of the solenoid to the other side of the potential source, a run relay winding for controlling said normally open switch, a circuit for energizing said run relay winding including a normally open manually operable switch and a second normally open relay-operated switch in series across the potential source, an antirepeat relay winding for controlling said second normally open relay-operated switch, a circuit for energizing the antirepeat relay winding including a normally open motor-energizing circuit relay operated switch and a normally closed manually operable switch connected in series across the potential source, a holding circuit for maintaining the antirepeat relay winding energized including a third normally open relay-operated switch and a normally closed press-operated limit switch in series across said normally closed, manually operable switch, means responsive to the energization of the antirepeat relay winding for closing said third normally open switch, a holding circuit for maintaining the run relay energized comprising a second press-operated limit switch connected across said second normally open relayoperated switch and said normally open, manually operable switch.

6. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press, a clutch and brake assembly adapted to be controlled selectively to engage the driving assembly with the clutch or brake of the clutch and brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, an energizing circuit for said motor, a source of potential, means for connecting the energizing circuit across the source of potential, means for connecting one end of the solenoid to one side of the potential source, a first normally open relay-operated switch for connecting the other side of the solenoid to the other side of the potential source, a run relay winding, means responsive to the energization of the run relay winding for closing said first normally open relay-operated switch, a circuit including said run relay winding, a manually operable normally open switch and a manually operable normally closed switch connected across the potential source for energizing the run relay winding, a shunt circuit for maintaining the run relay winding energized including a second normally open relay-operated switch and a press-operated limit switch connected in series across said normally open, manually operable switch, means responsive to the energization of the run relay winding for energizing said second normally open relay-operated switch, a third normally open relay operated switch, means responsive to the energization of the motor-energizing circuit for closing said third normally open relay operated switch, and means for connecting said third relay operated switch across said limit switch, said limit switch being set to close before bottom dead center and to open past bottom dead center of the press cycle, the construction being such, in event the main motor becomes tie-energized and said third relay operated switch is thus opened, the limit switch will maintain the run relay winding energized to permit the inertia of said flywheel to carry the press through bottom dead center.

7. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press, a clutch and brake assembly adapted to be controlled selectively to engage the driving assembly with the clutch or brake of the clutch and brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, a source of potential, means for connecting one end of the solenoid to one side of the potential source, a first normally open relay operated switch for connecting the other side of the solenoid to the other side of the potential source, 'a run relay winding, means responsive to the energization of the run relay Wll'ldlIlg for closing said first normally open relay-operated switch, a circuit for energizing said run relay winding comprising the run relay winding, a second normally open relay operated switch and a normally open, manually operable switch and a normally closed, manually operable switch in series across the potential source, an inching relay winding, means responsive to the energization of the inching relay winding for closing said second normally open relay operated switch, a circuit for energizing said inching relay winding comprising said normally closed, manually operable switch, a second normally closed, manually operable switch and the inching relay winding connected across the potential source in series, a holding circuit for maintaining the inching relay winding energized upon the opening of said second manually operable switch comprising a third normally open relay operated switch connected across said second manually operable switch, and means responsive to the energization of the inching relay winding for closing said third normally open relay operated switch, the construction being such that the opening of said normally closed first manually operable switch will de-energize the inching relay winding.

8. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press, a clutch and brake assembly adapted to be controlled selectively to engage the driving assembly with the clutch or brake of the clutch and brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, a potential source, means for connecting one end of the solenoid to one side of the potential source, a normally open first run relay-operated switch for connecting the other side of the solenoid to the other side of the potential source, a run relay winding, a circuit comprising a normally closed antirepeat relay-operated switch, a first normally open manually controlled switch, a second normally open manually controlled switch and the run relay winding connected in series across the potential source for energizing the run relay winding, a make circuit for the antirepeat relay winding including the antirepeat relay winding, a normally closed first manually operable switch-and a normally closed second manually operable switch connected across the potential source.

9. In a power press having a motor, a flywheel driven by the motor, a driving assembly for the press including a lubricated part, a pump for supplying oil to the lubricated part, an oil pump motor for operating the oil pump, a clutch and brake assembly adapted to be controlled selectively to engage the driving assembly with the clutch or brake assembly, a solenoid for exercising selective control over the clutch and brake assembly, a potential source, means for connecting one end of the solenoid to one side of the potential source, a normally open first run relay-operated switch for connecting the other side of the solenoid to the other side of the potential source, a run relay winding, an antirepeat relay winding, a circuit for energizing the run relay winding comprising the run relay winding, a normally open antirepeat relay-operated switch and a normally open manually operable switch in series across the potential source, a limit switch operated by the movement of the driving assembly, means for connecting the limit switch across the normally open manually operable switch contacts, a circuit for energizing the antirepeat relay winding comprising a normally closed manually operable switch and the antirepeat relay winding connected in series across the potential source, a holding circuit for maintaining the antirepeat relay winding energized when the normally closed manually operable switch is open, said holding circuit including a second normally open antirepeat relay switch and a second limit switch connected in series across the normally closed manually operable switch contacts, said second limit switch being operated by the movement of the driving assembly for the press, an oil safety relay winding for energizing the oil pump motor, an oil pressure switch adapted to close upon oil pressure, a circuit for energizing the oil safety relay winding including an oil pressure switch, the winding of the oil safety relay and a normally closed antirepeat relay-operated switch connected in series across the potential source, a holding circuit for maintaining the oil safety relay winding energized comprising a normaily open oil safety relay-operated switch connected across the normally closed antirepeat relay-operated Number switch. 598,459

References Cited in the file of this patent 5 UNITED STATES PATENTS Number Name Date 2,019,299 Fox et a1. Oct. 29, 1935 2,050,076 Wilrns Aug. 4, 1936 10 2,448,167 Baak Aug. 31, 1948 18 FOREIGN PATENTS Country Dat Great Britain Feb. 18, 

